Twelve studies were included. Nine studies (n=520) assessed helical CT and 5 studies (n=1,269) assessed V-P scanning; 2 studies assessed both techniques.
Eleven studies were prospective in design and one was retrospective. Four of the prospective studies reported that the enrolment of patients was consecutive. Verification bias was judged to be likely in 4 studies, while interpretation bias was thought to be absent in all but 2 studies.
Accuracy of helical CT (n=9): the sensitivity ranged from 53 to 100% and the specificity from 75 to 100%. The pooled sensitivity was 86% (95% confidence interval, CI: 80, 92) and the pooled specificity was 94% (95% CI: 91, 96).
Accuracy of V-P scanning, threshold 1 (n=5): the specificity ranged from 96 to 100%; the range in sensitivity was not reported. The pooled sensitivity was 39% (95% CI: 37, 41) and the pooled specificity was 97% (95% CI: 96, 98).
Accuracy of V-P scanning, threshold 2 (n=5): the sensitivity ranged from 54 to 100%; the range in specificity was not reported. The pooled sensitivity was 86% (95% CI: 83, 89) and the pooled specificity was 46% (95% CI: 44, 47).
Accuracy of V-P scanning, threshold 3 (n=5): the sensitivity ranged from 98 to 100%; the range in specificity was not reported. The pooled sensitivity was 98% (95% CI: 97, 100) and the pooled specificity was 4.8% (95% CI: 4.7, 4.9).
No significant predictors were found in the separate univariate analysis for CT or V-P scanning, and none remained significant in the final multivariate model that included the dummy variable for test type. The test comparison showed that helical CT was superior to V-P scanning at threshold 2 (P<0.001), and suggested that it was also superior at threshold 3 (P=0.05) and that there was no significant difference between helical CT and V-P scanning at threshold 1 (P=0.457). The sensitivity analysis, in which studies of CT published before 1995 were excluded, found similar results when these studies were included.